hepatitis C essays

hepatitis C essays Hepatitis C is a liver disease that is caused by the hepatitis C virus (HCV). The virus enters the liver cells, uses the cell's inner genetic machinery to make copies of itself, which then infect more cells. In about 15% of cases, hepatitis C infection is cleared spontaneously by the body and there are no long-term consequences. Unfortunately, in the majority 85%, of cases the infection becomes chronic and slowly damages the liver over many years. Over time, this liver damage can lead to scarring of the liver, end-stage liver disease, and liver cancer. Hepatitis C is spread through exposure to HCV-infected blood this may occur through IV drug use, a transfusion with HCV infected blood, contaminated hemodialysis equipment, unprotected sex, needlestick injuries, and contaminated tattooing or body piercing equipment. People with hepatitis C infection usually do not have characteristic disease symptoms. When symptoms do appear, they may be vague and include tiredness, stomach pain, and rash. Because HCV infection often has no symptoms, many people do not know they have hepatitis C and may be infecting others. The only way to know whether you have hepatitis C is to get a blood test for hepatitis C. It is estimated that about 4 million people in the United States are infected with hepatitis C, which is about 2% of the population. This makes hepatitis C much more common than HIV infection. About 2.7 million Americans had chronic hepatitis C infection in the early 1990s, which means they could not clear the virus on their own. This number is expected to increase to 10.8 million in the next 10 to 12 years. Each year, there are about 35,000 cases of acute hepatitis C. Chronic hepatitis C infection is more common in certain groups, such as the homeless, Vietnam War veterans, the prison population, and hemophiliacs. The incidence is high in these groups because they are more likely to have the hepatitis C risk factors. The hig...

Facts of the Pre-Historic Predator Hyaenodon

Facts of the Pre-Historic Predator Hyaenodon Name: Hyaenodon (Greek for hyena tooth); pronounced hi-YAY-no-don Habitat: Plains of North America, Eurasia, and Africa Historical Epoch: Late Eocene-Early Miocene (40-20 million years ago) Size and Weight: Varies by species; about one to five feet long and five to 100 pounds Diet: Meat Distinguishing Characteristics: Slender legs; large head; long, narrow, tooth-studded snout About Hyaenodon The unusually long persistence of Hyaenodon in the fossil recordvarious specimens of this prehistoric carnivore have been found in sediments dating from 40 million to 20 million years ago, all the way from the Eocene to the early Miocene epochscan be explained by the fact that this genus comprised a large number of species, which ranged widely in size and enjoyed a nearly worldwide distribution. The largest species of Hyaenodon, H. gigas, was about the size of a wolf, and probably led a predatory wolf-like lifestyle (supplemented with hyena-like scavenging of dead carcasses), while the smallest species, the appropriately named H. microdon, was only about the size of a house cat. You might assume that Hyaenodon was directly ancestral to modern wolves and hyenas, but youd be wrong: the hyena tooth was a prime example of a creodont, a family of carnivorous mammals that arose about 10 million years after the dinosaurs went extinct and went extinct themselves about 20 million years ago, leaving no direct descendants (one of the biggest creodonts was the amusingly named Sarkastodon). The fact that Hyaenodon, with its four slender legs and narrow snout, so closely resembled modern meat-eaters can be chalked up to convergent evolution, the tendency for creatures in similar ecosystems to develop similar appearances and lifestyles. (However, bear in mind that this creodont didnt much resemble modern hyenas, except for the shape of some of its teeth!) Part of what made Hyaenodon such a formidable predator was its almost comically oversized jaws, which had to be supported by extra layers of musculature near the top of this creodonts neck. Like roughly contemporary bone-crushing dogs (to which it was only distantly related), Hyaenodon would likely snap the neck of its prey with a single bite, and then use the slicing teeth in the back of its jaws to grind down the carcass into smaller (and easier to handle) mouthfuls of flesh. (Hyaenodon was also equipped with an extra-long palate, which allowed this mammal to continue breathing comfortably as it dug into its meal.) What Happened to Hyaenodon? What could have edged Hyaenodon out of the spotlight, after millions of years of dominance? Thebone-crushing dogs referenced above are possible culprits: these megafauna mammals (typified by Amphicyon, the bear dog) were every bit as lethal, bite-wise, as Hyaenodon, but they were also better adapted for hunting scurrying herbivores across the wide plains of the later Cenozoic Era. One can imagine a pack of hungry Amphicyons denying a Hyaeonodon its recently killed prey, thus leading, over thousands and millions of years, to the eventual extinction of this otherwise well-adapted predator.